You may want to just use something like a 9V memory saver (it plugs into the cigarette lighter) or, if you have a booster pack, you could also use that. You could also purchase a small 9V battery, attach two leads and then connect to your battery leads before disconnecting. If none of the above are suitable then there are quite a few sites that will (for a price) give you your code from the 14 digit serial number on the radio.